ipa-graceperiod: fix memory leaks

Direct return of invalid grace limit bypassed cleanup code.
`tmpstr` variable was not freed in all code paths.

Related: https://pagure.io/freeipa/issue/9895
Signed-off-by: Viktor Ashirov <vashirov@redhat.com>
Reviewed-By: Rob Crittenden <rcritten@redhat.com>
Reviewed-By: Alexander Bokovoy <abbra@users.noreply.github.com>

daemons/ipa-slapi-plugins/ipa-graceperiod/ipa_graceperiod.c

@@ -448,7 +448,8 @@ static int ipagraceperiod_preop(Slapi_PBlock *pb)
         goto done;
     } else if (grace_limit < -1) {
         LOG_FATAL("Invalid passwordGraceLimit value %ld\n", grace_limit);
-        return LDAP_OPERATIONS_ERROR;
+        ret = LDAP_OPERATIONS_ERROR;
+        goto done;
     }
 
     grace_user_time = slapi_entry_attr_get_int(target_entry, "passwordGraceUserTime");
@@ -500,6 +501,7 @@ done:
         slapi_vattr_values_free(&values, &actual_type_name, attr_free_flags);
     }
     if (sdn) slapi_sdn_free(&sdn);
+    slapi_ch_free_string(&tmpstr);
 
     LOG("preop returning %d: %s\n", ret, errstr ? errstr : "success\n");